ML20211L215

Safety Evaluation Supporting Licensee Relief Request,Per 10CFR50.55a(a)(3)(i)

ML20211L215
Person / Time
Site:	Byron
Issue date:	10/03/1997
From:	NRC (Affiliation Not Assigned)
To:
Shared Package
ML20211L184	List: ML20211L179 ML20211L215
References
NUDOCS 9710100136
Download: ML20211L215 (4)

Text

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NUCLEAR REGULATORY COMMIE 810N

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RE0 VEST FOR TEMPORARY REllEF FROM ASME CODE. SECTION IIh REQUIREMENTS FOR THE USE OF LINE STOPPING EQUIPMENT ON FSSENTIAL SERVICE WATER FOR ASME CLASS 3 PIPING COMMONWEALTH EDISON COMPANY I

BYRON STATION. UNITS 1 AND 2 DOCAET NOS. STN 50-454 AND STN 50-455

1.0 INTRODUCTION

, the By letter dated licensee /r 11Station, of Byron 11,1997, Commonwealth Units Edison Company 1 and 2 requested temporary(Comed)frelie from the requirements of the 1974 Edition of the kmerican Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (Code), Section !!!, in order to temporarily install inecharical line stopping equipment in individual 24" diameter Essential Service Water (SX) coolin" tower cell return piping lines.

The piirpore of the line stopping equipment wIll be to tem)orarny isolate SX riser piping and its associtted coolin tower cell from tie remainin seven cooling tower cells and basin. This w 11 allow for replacement of the existing 24" diameter carbon steel riser piping with stainless steel piping .'

and to allow for the replacement and refurbishment of ear.h corresponding riser

. Isolation motor-operated valve (OSX163A-H). Additional information was

submitted by letter dated July 10, 1997.

The licensee is planning for the piping replacement because it has been determined that th3 minimum remaining life for the carbon steel riser piping in Byron Station is approximately 5 years. In addition, all eight riser isolation valves have started to show degraded performance in isolating individual SX riser lines, particularly during winter operation. Installation

, of stainless steel riser piping and replacement / refurbishment of the riser isolation vdas would significantly improve the material condition of the SX cooling war piping and improve the operation of the cooling tower riser isolation valve:;

-The relief is requested for eight temporary >eriods, during which the eight riser isolation valves (OSX163A-H) will be cianged out and the eight sections of riser piping will be replaced. The temporary line stopping eouipment will, therefore, be installed sequentially in each of the eight SX piping lines, over a period of approximately four to five days for each line stop iteration.

The licensee anticipates that the scheduled temporary line stop insta11 Cion 9710100136 971003 PDR ADOCK 05000454

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• and piping replacement work will occur over a period of approximately 36 months, with the work planned for spring and fall non-outage periods.

2.0 EVALUATION 2.1 Comoonent for Which Relief is Reauired The SX cooling tower return piping components for which temporary relief is requested are piping lines OSX97AA-24, OSX97AB-24, OSX97AC-24, OSX97AD-24, OSX97AE-24, OSX97AF-24, OSX91AG-24, and OSX97AH-24. The lines run underground between the Auxiliary Building and the SX Cooling Tower Basin, raturning SX system water from the plant to the basin. The affected piping components provide a passive pressure boundary for the SX Cooling Tower at Byron Station, .

in accordance with the requirements of ASME Code,Section III, Class 3. The l SX Cooling Tower Basin is the primary source of the ultimate heat sink (VHS).

for Byron Station.

2.2 Code Reauirement From Which Relief is Reauested The affected components, as previously listed, are constructed to meet the requirements of the ASME Code, Section !!!,1974 Edition, up to and including Summer 1975 Addenda. Article NA-3700 requires material manufacturers and suppliers to have a Quality System Certificate and Certified Materials Test Reports. Article ND-2100 requires that pressure retaining materials conform to the requirements of Tables I-7.0 and I-8.0 of Appendix I and requires that a Certified Material Test Report be provided. Article ND-3100 defines the loading criteria for the plant design conditions. In particular, subarticle designof(components.ND-3112.3 Article ND-3500b) requires theuse requires the effects of ASMEof earthquakes material to be conside specifications for valves. Article ND-4100 requires the component manufacturer to certify by application of the appropriate Code symbol and completion of the appropriate Data Report in accordance with NA-8000.

Finally, ND-4100 also requires certification of treatments, tests, and examinations.

2.3- Pronosed Alternative to Code Reautrements As an alternative to the ASME Code,Section III, requirements, the licensee proposed to install temporary line stopping equipment which is designed and built to meet tFe temperature and pressure requirements of ANSI B16,5, Class 150. The line stopping equipment will be provided by TDW Services, Inc., a vendor certified to 9001 and 9002 Quality System of International Organization for Standardization. TDW Services is the only hot ta) ping and pluning company in the world that is known to have obtained tits quality control certification.

In addition, Byron Station will implement a compensatory action, during the temporary line stop installation, to maintain elevated water levels in the SX Cooling Tower Basin, to ensure that sufficient water is available to mitigate the consequences of a temporary line stop failure. Finally,thoroughjob

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on-line risk assessment, and operator briefing will be implemented l planning, for each iteration of the temporary condition to enhance overall plant safety.  !

, This will ensure that operators are fully aware of the necessary actions to be

!- taken following a postulated failure of the line stop to provide cooling tower  ;

d riser piping isolation. j 2.4 Basis for Relief a

Pursuant the basis to 10the that CFR propose50.55a(d)(3)(1), the provide alternatives licenseean requested acceptable temporary level ofrelief on i quality and safety. The licensee stated that the ttmporary line stopping j equipment provides an equivalent alternative to the requirements of ASME Code, l Section Ill, for the planned temporary iterations, f line stopping equi by t roposedtemporarferpressuresthantkmenthasbeendesinedandtested, The$evendor to hig emaximumanticipafedpressurein the riser pip ng, at the location of the temporary line stop installation.

For the antic pated SX system operatin configuration, the calculated maximum 3 differential pressure across the nearb downstream riser isolation valves 1

(0$X163A-H) of 150 psig for the 24" diameter line stop plugginis head. It 26ispsig, also which less is signi icantl l

than the maximum rated working pressure of 275 psi for the line stop sandwich i valve, hot tapping machine, plugginfi machine, and 6" diameter temporary

! flange plug. The line stopping equ'pment is rated for a maximum temperature i of 180 degrees Fahrenheit. The $X piping was originally qualified to a design pressure of 125 psig and a design temperature of 140 degrees Fahrenheit which

are well bounded by the rated capabilities of the line stopping equipment.

l This is found acceptable to the staff. ,

i The licensee stated that post-installation verification for the integrity of

! line stopping equipment will be performed prior to removing the riser

[ isolation valves (0SX163A-H and-their associated downstream piping. The line

- stopping equipment will be s)eismically restrained to prevent damaging the-safety related SX piping system during a design basis earthquake. In

addition, ASME Code Section Ill, Class 3 blind flanges will be available onsite to be installed in place of the line stopping equipment,'in the event

j. of a failure of the equipment while isolation of the cooling tower return line 2

is required. A special procedure will also be implemented which directs the

work activities and arovides guidance to station operators for the appropriate

actions to take in tie event of such failure. This is also acceptable to the j staff.

2.5 Onerability of the SX System durina Renairs

] 'It is noted that the ultimate heat sink for Byron Station is required to be j operable in all modes of operation. The Byron Ststion technical specifications (TS) do not allow either tenin (A or B) of the SX Cooling Tower to be isolated for an extended period, to allow for the completion of the.

scheduled installation and re>1acement work, without having to shut down both units. The licensee stated tiat there is no existing isolation capability for

. -4 the subject riser piping. Also, there are no line stop vendors that can provide their equipment as ASME Code, Section Ill, Class 3 material.

Therefore, relief from the requirements of ASME Code, Section !!!, is required to perfom the isolation activities. Delaying or not performing such activities would lead to an eventual deterioration in the material condition of the SX cooling tower riser piping, and consequently a not decrease in plant quality. .

In its submittal dated July 10, 1997, the licensee provided additional infomation to address operability of the SX system while repairs are being made. The licenses stated that operability of the SX system will be maintained throughout the repair period in accordance with the Byron TS, and that the operable sections of the SX system will continue to satisfy system design-basis requirements. Byron TS 3/4.7.5.b requires in part, that a total of six fans to be operable. Consequently,uptotwocellscanbeunavailable with the UHS remaining operable. The licensee stated that the modification  ;

work will affect only one cell at a time with the installation of the linestop '

device in the branch connection betwecn the return header and the riser isolation valve. The licensee has adequately addressed system operability considerations and no,further action in this regard is required.

3.0 CONCLUSION

Based on the above information provided by the licensee, the staff concludes that the licensee's relief request may be authorized pursuant to 10 CFR 50.55a(a)(3)(1) in that the proposed alternative temporary installation of i line stopping equipment provides an acceptable level of quality and safety, with respect to the requirements of ASME Code,Section III.

Principle Reviewers: A. J. Lee J. E. Tatt!m #

Date: October 3, 1997-

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